Konjiki no Yami, or Golden Darkness, is an extraterrestrial assassin whose abilities allow her to transform her body parts into a variety of objects, notably weapons used in her assassinations. She is very powerful in battle, easily defeating both living and mechanical opponents.

Yami is very introverted and soft-spoken, opening up very slowly even when showered with kindness. Her greatest dislike is "ecchi" or perverted people, whom she holds the utmost hatred for, not hesitating to punish anyone she deems immoral.

When she accidentally encounters a would-be target of her assassination on the street and gets treated to some tasty taiyaki, she begins to doubt her mission. To begin with, the target tried to cheer her up 'because she looked lonely.' When the truth behind her assignment is revealed, Konjiki no Yami reconsiders the path she wants to take. As an assassin, and as a person.

Yami could get used to life on Earth, full of unknowns as it is to her. There is just one problem – the lack of job opportunities for people whose only job experience is in assassination.